Solution and process for the pre-treatment of copper surfaces using an N-alkoxylated adhesion-promoting compound

ABSTRACT

The invention concerns a solution for pretreating copper surfaces, and a method for pre-treating copper surfaces allowing the formation of a tight bond to plastic substrates. The solution comprises: a) hydrogen peroxide, b) at least one acid, and c) at least one nitrogen-containing, five-membered, heterocyclic compound, and d) additionally at least one nitrogen containing, adhesion-promoting compound, said compound comprising, or consisting of, lactams, non-quaternary fatty amines, amides and polyamides, connected at one or more of its nitrogen atoms with at least one residue of formula (I).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase of International ApplicationNo. PCT/EP2011/068510, filed Oct. 24, 2011, which claims priority toEuropean Patent Application No. 10190611.3, filed Nov. 10, 2010, thecontents of each are hereby incorporated by reference in theirentireties.

The invention concerns a solution and a process to pretreat coppersurfaces so that a tight bond can be subsequently formed between thepretreated copper surfaces and plastic substrates. The solutionpreferably serves to pretreat copper-coated inner layers of printedcircuit boards to subsequently allow a tight bond between the innerlayers of the printed circuit board and the board's inner layers made ofartificial resins.

In manufacturing printed circuit boards, various steps are carried outin which copper surfaces must be tightly bonded to an organic substrate.In some cases, the required adhesion of the formed bonds must be ensuredover a long period. In other cases, a tight bond only has to exist for ashort period, e.g. when the organic substrate only remains on the coppersurfaces during manufacture of the printed circuit board. For example,the tight bond of dry film plating resists (for structuring conductorlines on printed circuit boards) to the copper surfaces only has toexist while manufacturing the printed circuit board. After the conductorline structures are formed, the resists can be removed.

The easiest way to increase the adhesion is to etch and hence roughenthe copper surfaces before forming the bond. Microetching solutions areused such as sulfuric acid solutions of hydrogen peroxide or sodiumperoxodisulfate.

Another procedure is described in U.S. Pat. No. 3,645,772. Apretreatment solution is used for the copper surfaces that e.g. contains5-aminotetrazole.

Long-term stability is especially necessary when laminating multilayerprinted circuit boards. Other treatments for the copper surfaces arerequired in this case.

When manufacturing multilayer boards, several inner layers are laminatedto insulating artificial resin layers (so-called prepregs: e.g., epoxideresin films reinforced with fiberglass nets). The inner bonds of thelaminate must hold throughout the entire life of the printed circuitboard. The copper layers (preferably the conductor line structures) onthe inner layers must be surface-treated. Various procedures have beendeveloped to solve this problem.

The normal procedure for pretreating the materials before lamination isto form an oxide layer on the copper surfaces. In this process, known asthe brown or black oxide process, very aggressive reaction conditionsare used to form the oxide. A disadvantage of this procedure is that theoxide layer used for enhancing adhesion to the artificial resin layer isnot very resistant to acid and especially to hydrochloric treatmentsolutions. They are hence attacked in subsequent processes for platingthe through-holes in the boards. The adhesive bond is eliminated, anddelamination occurs at the attacked sites (pink ring: Anexternally-visible attack on the black oxide layer directly next to ahole in printed circuit boards with the discoloration of the originallyblack oxide layer. The pink copper coating of the inner layer isrecognizable as an annular defect; wedge void: A defect (recognizable ina micrograph of a treated hole) in a printed circuit board in the formof a crack between a copper inner layer and the neighboring printedcircuit board resin from the attack of acid treatment solutions on theblack oxide layer).

The above-cited problem is solved by reducing the oxide layer surfacebefore lamination. The reduced black oxide is more stable than normalblack oxide against chemicals used in plating the through-holes. Theadditional reduction step costs a great deal, however. In addition, thechemicals used for reduction are not very resistant to oxidation fromair, so that the useful life of the baths and storage life of thesupplementary chemicals are limited. An attempt to eliminate thisproblem is made in JP A 08097559. The reduced copper oxide layers areprovided with a protective layer by treating them with an aqueoussolution containing an aminothiazole and/or aminobenzothiazole compound.However, the problems of expensive reduction chemicals, their lowresistance to oxidation and the layer's sensitivity to acid are notcompletely eliminated.

Another option for promoting adhesion is to treat the copper surfaceswith an aqueous or alcoholic solution of an azole compound. Such aprocedure is e.g. presented in WO 96/19097 A1. The copper surfaces aretreated with a solution that contains 0.1-20 weight percent hydrogenperoxide, an inorganic acid (e.g. sulfuric acid), an organic corrosioninhibitor (e.g. benzotrizole), and a wetting agent. The hydrogenperoxide etches the copper surface to produce microrough surfaces.

U.S. Pat. No. 4,917,758 discloses etching solutions that, however, serveto etch copper cladding on the materials of the printed circuit board.Hydrogen peroxide, sulfuric acid and a nitrogen-containing compound(preferably amino benzoic acid, amino tetrazole or phenylurea) are alsoin these solutions.

U.S. Pat. No. 5,869,130 describes a process for treating metal surfaceswith a composition comprising an oxidizer, an acid, a corrosioninhibitor, a source of halide ions and optionally a water solublepolymer in order to increase the adhesion of polymeric materials to themetal surface. Most preferably, the water soluble polymer is a polymerof ethylene oxide, an ethylene oxide-propylene oxide copolymer,polyethylene glycols, polypropylene glycols or polyvinyl alcohols. Suchpolymers decompose rapidly in said composition, leading to a stronglydecreasing peel strength during the process.

WO9940764 concerns solutions for the preliminary treatment of coppersurfaces which are subsequently to be firmly bonded to organicsubstrates. The solution is used, in particular, for firmly bondinglaminated multilayered printed circuit boards and for firmly bondingresists to the copper surfaces of printed circuit boards. The solutionscontain (a) hydrogen peroxide; (b) at least one acid; (c) at least onenitrogen-containing, five-membered heterocyclic compound which does notcontain any sulphur, selenium or tellurium atom in the heterocycle; and(d) at least one adhesive compound from the group consisting of sulfinicacids, seleninic acids, tellurinic acids, which are not identical to theacid (b), heterocyclic compounds containing at least one sulphur,selenium and/or tellurium atom in the heterocycle, and sulfonium,selenonium and telluronium salts. Moreover, WO9940764 describes aprocess to pretreat copper surfaces to allow a tight bond to besubsequently formed between the copper surfaces and plastic substratesin which the copper surfaces are brought into contact with theabove-mentioned solution.

WO9940765 describes, in comparison to WO9940764, an alternative processfor the preliminary treatment of copper surfaces which are subsequentlyto be firmly bonded to organic substrates. Copper surfaces are firstbrought into contact with a first solution containing hydrogen peroxide,at least one acid and at least one nitrogen-containing, five-memberedheterocyclic compound which does not contain any sulphur, selenium ortellurium atom in the heterocycle. The copper surfaces are then broughtinto contact with a second solution containing at least one adhesivecompound from the group consisting of sulfinic acids, seleninic acids,tellurinic acids, heterocyclic compounds containing at least onesulphur, selenium and/or tellurium atom in the heterocycle, as well assulfonium, selenonium and telluronium salts. The process is used, inparticular, for firmly bonding laminated multilayered printed circuitboards and for firmly bonding resists to the copper surfaces of printedcircuit boards.

The object of the present invention was to provide a pretreatmentsolution and a process that can create a tight bond between the coppersurfaces and plastic surfaces. A higher peel strength should be reachedthat is stable during the whole process. The process should be simple,easy to use, and inexpensive. It is also important that treatment withthe solutions produce a material bond that is not problematic (no pinkring, wedge voids or resin flaws) in the subsequent printed circuitboard manufacturing processes, e.g. plating through-holes in boardmaterials. The used pretreatment solutions should therefore be suitablefor manufacturing printed circuit boards.

These problems are is solved by the pretreatment solution cited in claim1 and the treatment process cited in claim 8.

The pretreatment solution according to the invention is for pretreatingcopper surfaces to allow a tight bond to be formed with plasticsubstrates, and it comprises:

-   -   a) hydrogen peroxide,    -   b) at least one acid, and    -   c) at least one nitrogen-containing, five-membered, heterocyclic        compound    -   and    -   d) additionally at least one nitrogen containing,        adhesion-promoting compound selected from the group comprising,        or consisting of, lactams, non-quaternary fatty amines, amides        and polyamides, which is connected at one or more of its        nitrogen atoms with at least one residue of formula (I)

-   -   wherein    -   n is an integer from 1 to about 100,    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms, and    -   each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can be selected        independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—        moiety,    -   with the proviso that the nitrogen-containing, five-membered,        heterocyclic compound selected for component c) is not connected        at any of its nitrogen atoms with a residue of formula (I).

With the pretreatment solution and the process of the invention a peelstrength that is comparable to peel strengths known from the state ofthe art can be reached at lower etch depths than in the state of theart, which means shorter processing times and economic benefit.

The expression “at least one nitrogen containing, adhesion-promotingcompound selected from the group comprising, or consisting of, lactams,fatty amines, amides and polyamides” means mixtures of differentlactams, different fatty amines, different amides, and differentpolyamides as well as mixtures of two or more of a lactam,non-quaternary fatty amine, amide and polyamide.

Adhesion-promoting compounds are to be selected that are sufficientlysoluble in the acidic, preferably sulfuric acid solution.

The pretreatment solution according to the invention, containingcomponents a)-d), is hereinafter also abbreviated as “solution”.

The problem on which the invention is based is solved in particular bythe use of the solution according to claim 15, wherein the solution isused in the pre-treatment of printed circuit board inner layers, whichhave copper layers, for the formation of a firmly adhesive bondingbetween the printed circuit inner layers and synthetic resin layers. Thecited solution is preferably used to pretreat copper-coated inner layersof printed circuit boards to allow a tight bond to be formed between theinner layers of the printed circuit boards and plastic resin layers.

The cited solution can also be used for the pre-treatment of printedcircuit boards, which have copper layers, for the formation of a firmlyadhesive bonding between the copper layers and resists formed fromplastic materials.

The present invention moreover discloses the use of the compound d) asdefined above for for preparing a solution for the pre-treatment ofprinted circuit board inner layers, which have copper layers, for theformation of a firmly adhesive bonding between the printed circuit innerlayers and synthetic resin layers.

Preferred embodiments of the invention are found in the dependentclaims.

The nitrogen-containing, five-membered, heterocyclic compound selectedfor component c) of the solution is not identical to thenitrogen-containing, adhesion-promoting compound selected for componentd). There is at least the difference that the nitrogen-containing,five-membered, heterocyclic compound selected for component c) is notconnected at any of its nitrogen atoms with a residue of above-citedformula (I).

In the present invention the term “aliphatic” means a hydrocarbon moietycharacterized by a straight or branched chain arrangement of constituentcarbon atoms and may be saturated or partially unsaturated with one, twoor more double or triple bonds.

For the purpose of the present invention the term “alkyl” means amonovalent linear or branched saturated hydrocarbon moiety, having inthe skeleton thereof but carbon atoms, wherein an alkyl moiety comprisesall conceivable isomers thereof. For example, C1-C6 alkyl means methyl,ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl,isopentyl, tert-pentyl, neo-pentyl, hexyl, 2-methyl pentyl, 3-methylpentyl, 2,3-diethyl butyl and C1-C4 alkyl means methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl.

For the purpose of the present invention the term “alkylene” means adivalent linear or branched saturated hydrocarbon moiety, having in theskeleton thereof but carbon atoms, wherein an alkylene moiety comprisesall conceivable isomers thereof.

The term “cycloalkyl” means a monovalent saturated or partiallyunsaturated, non-aromatic, carbocyclic moiety consisting of mono- orbicyclic rings. Cycloalkyl can optionally be substituted with one ormore substituents, wherein each substituent is independently hydroxy,alkyl, alkoxy, halo, haloalkyl, amino, monoalkylamino, or dialkylamino,unless otherwise specifically indicated. Examples of cycloalkyl moietiesinclude, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl,cyclohexyl, cycloheptyl, and the like, including partially unsaturatedderivatives thereof such as cyclohexenyl, cyclopentenyl, and the like.

The term “cycloalkylene” means a divalent saturated or partiallyunsaturated, non-aromatic, carbocyclic moiety consisting of mono- orbicyclic rings. Cycloalkyl can optionally be substituted with one ormore substituents, wherein each substituent is independently hydroxy,alkyl, alkoxy, halo, haloalkyl, amino, monoalkylamino, or dialkylamino,unless otherwise specifically indicated.

For the purpose of the present invention the term “alkenyl” means amonovalent linear or branched unsaturated hydrocarbon moiety, having inthe skeleton thereof but carbon atoms, wherein an alkyl moiety comprisesall conceivable isomers thereof.

“Aryl” means a monovalent cyclic aromatic hydrocarbon moiety consistingof a mono-, bi- or tricyclic aromatic ring. The aryl group can beoptionally substituted. Examples of aryl moieties include, but are notlimited to, phenyl, naphthyl, naphthalenyl, phenanthryl.

“Arylene” means a divalent cyclic aromatic hydrocarbon moiety consistingof a mono-, bi- or tricyclic aromatic ring. The arylene group can beoptionally substituted.

As to formula (I) n is an integer from 1 to about 100, preferably 1 toabout 50.

As stated above, each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can beselected independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—moiety. Thereby, block-copolymer and random copolymer structures canoccur. A block copolymer structure can for example occur, if first—(CHR₁—CHR₂—O)— moieties follow to each other, followed by second—(CHR₁—CHR₂—O)— moieties, wherein in the first moieties R₁ and/or R₂ aredifferent from R₁ and/or R₂ in the second moieties.

R₁ is in one embodiment selected from hydrogen, alkyl, phenyl. R₁ ispreferably C₁-C₄ alkyl or hydrogen, still more preferably methyl orethyl or hydrogen, and most preferably methyl or hydrogen, and these canbe combined with all above-cited values for n.

R₂ is in one embodiment selected from hydrogen, alkyl, phenyl. R₂ ispreferably C₁-C₄ alkyl or hydrogen, still more preferably methyl orethyl or hydrogen, and most preferably methyl or hydrogen, and these canbe combined with all above-cited values for n and all above-cited R₁.

In one embodiment, which can be combined with all above-cited values forn, R₁ in the residue of formula (I) is hydrogen and R₂ is a hydrocarbonresidue with 1 to about 6 carbon atoms, preferably alkyl or phenyl, morepreferably C₁-C₄ alkyl, still more preferably methyl or ethyl, and mostpreferably methyl. As stated above, each R₁ and R₂ in a —(CHR₁—CHR₂—O)—moiety can be selected independently of each R₁ and R₂ in another—(CHR₁—CHR₂—O)— moiety. In a special embodiment, R₁ in all—(CHR₁—CHR₂—O)— moieties is hydrogen and R₂ in all —(CHR₁—CHR₂—O)—moieties is methyl. In another special embodiment, R₁ in all—(CHR₁—CHR₂—O)— moieties is hydrogen and R₂ in all —(CHR₁—CHR₂—O)—moieties is ethyl.

In another embodiment, which can be combined with all above-cited valuesfor n, R₁ in formula (I) is a hydrocarbon residue with 1 to about 6carbon atoms, preferably alkyl, or phenyl, more preferably C₁-C₄ alkyl,still more preferably methyl or ethyl, and most preferably methyl, andR₂ is hydrogen. In a special embodiment, R₂ in all —(CHR₁—CHR₂—O)—moieties is hydrogen and R₁ in all —(CHR₁—CHR₂—O)— moieties is methyl.In another special embodiment, R₂ in all —(CHR₁—CHR₂—O)— moieties ishydrogen and R₁ in all —(CHR₁—CHR₂—O)— moieties is ethyl.

In a further embodiment, which can be combined with the aforementionedembodiments, R₁ plus R₂ contain 6 carbon atoms in maximum, morepreferably 4 carbon atoms in maximum.

In a highly preferred embodiment R₁ is hydrogen or methyl and R₂ ishydrogen or methyl, wherein each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moietycan be selected independently of each R₁ and R₂ in another—(CHR₁—CHR₂—O)— moiety, and with the proviso that, in each moiety, R₁ ishydrogen if R₂ is methyl, and with the proviso that R₂ is hydrogen if R₁is methyl.

In another highly preferred embodiment, R₁ and R₂ in all —(CHR₁—CHR₂—O)—moieties are hydrogen.

In view of the above disclosure, the residue of formula (I) is in highlypreferred embodiments a polyethylene glycol (PEG) or a polypropyleneglycol (PPG) residue.

The invention also discloses a pretreatment solution for pretreatingcopper surfaces to allow a tight bond to be formed with plasticsubstrates, which comprises:

-   -   a) hydrogen peroxide,    -   b) at least one acid, and    -   c) at least one nitrogen-containing, five-membered, heterocyclic        compound    -   and    -   d) additionally at least one nitrogen containing,        adhesion-promoting compound, obtainable, or obtained, by        alkoxylation of a lactam, fatty amine, amide or polyamide with        one or more compounds of formula (Ia),

-   -   wherein    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms, and    -   with the proviso that the nitrogen-containing, five-membered,        heterocyclic compound selected for component c) is not        alkoxylated at any of its nitrogen atoms with a compound of        formula (Ia), and that the product obtainable, or obtained, by        alkoxylation of a fatty amine is a non-quaternary fatty amine.

R₁ in formula (Ia) is in one embodiment selected from hydrogen, alkyl,phenyl. R₁ is preferably C₁-C₄ alkyl or hydrogen, still more preferablymethyl or ethyl or hydrogen, and most preferably methyl or hydrogen.

R₂ in formula (Ia) is in one embodiment, which can be combined with theall embodiments of R₁, selected from hydrogen, alkyl, phenyl. R₂ ispreferably C₁-C₄ alkyl or hydrogen, still more preferably methyl orethyl or hydrogen, and most preferably methyl or hydrogen.

In one embodiment, one of R₁ or R₂ in formula (Ia) is hydrogen and theother is a hydrocarbon residue with 1 to about 6 carbon atoms,preferably alkyl or phenyl, more preferably C₁-C₄ alkyl, still morepreferably methyl or ethyl, and most preferably methyl.

In another preferred embodiment, R₁ and R₂ in formula (Ia) are hydrogen.

Preferred compounds of formula (Ia) contain 2 to about 8 carbon atoms,and most preferred are ethylene oxide (also called oxyethylene),propylene oxide (also called oxypropylene), 1-butylene oxide, 2-butyleneoxide, or styreneoxide.

The term alkoxylation means reacting nitrogen atom(s) of a lactam,polyamide or fatty amine with a compound of formula (Ia). Thus,alkoxylation in the present invention means N-alkoxylation. Thus, analkoxylated lactam, polyamide, fatty amine, or amide is the reactionproduct which can be obtained by alkoxylation of the respectivecompound. Alkoxylation is known to a person skilled in the art andwidely described in scientific and patent literature.

Alkoxylated lactams, fatty amines, amides or polyamides can be preparedby using more than one compound of formula (Ia) for alkoxylation.Alkoxylated lactams, fatty amines, amides or polyamides can be preparedby sequential alkoxylation with two or more of the aforementionedcompounds, as for example described in U.S. Pat. No. 6,552,091.

The nitrogen containing, adhesion-promoting compound can be selectedfrom one or more of alkoxylated lactams, alkoxylated fatty amines,alkoxylated amides and alkoxylated polyamides, wherein alkoxylation wasperformed with one or more compounds of formula (Ia).

In one embodiment, the nitrogen-containing, adhesion-promoting compoundselected for component d) of a solution of the invention is a lactam offormula (II)

-   -   wherein    -   n is an integer from 1 to about 100,    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can be selected        independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—        moiety, and    -   R₃ is a hydrocarbon residue with 2 to about 20 carbon atoms.

With respect to special embodiments and combinations of n, R₁ and R₂ itis referred to the above disclosure as to formula (I).

In one embodiment, which can be combined with all special embodimentsand combinations of n, R₁ and R₂, R₃ is C₂-C₂₀-alkylene, preferablyC₂-C₁₂-alkylene, unsubstituted or substituted by 1, 2, 3, 4, 5 or 6substituents selected independently of one another from the groupconsisting of alkylene, cycloalkylene and arylene.

In a preferred embodiment, R₃ is an alkylene residue of the formula—(CH₂)_(y)—, wherein y is an integer from 2 to about 20, more preferably2 to about 12, and most preferably 2 to about 7.

In a very preferred embodiment, the lactam selected for component d) ofthe solution is ethoxylated beta-propiolactam,hexaethoxylated-gamma-butyrolactam, octaethoxylated-delta-valerolactam,pentapropoxylated-delta-valerolactam,hexaethoxylated-epsilon-caprolactam,dodecaethoxylated-epsilon-caprolactam, or a mixture of two or more fromthese compounds.

Suitable lactams of formula (II) are described in DE3836521, which isincorporated by reference in its entirety.

In a further embodiment, the nitrogen-containing, adhesion-promotingcompound selected for component d) of a solution of the invention is apolyamide of formula (III)

-   -   wherein    -   n is an integer from 1 to about 100,    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can be selected        independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—        moiety,    -   R₃ is a hydrocarbon residue with 1 to about 20 carbon atoms,    -   each R₃ in a —(N—R₃—CO)— moiety can be selected independently of        each R₃ in another —(N—R₃—CO)— moiety, and    -   each n in a —(CHR₁—CHR₂—O)_(n)— moiety or chain can be selected        independently of each n in another —(CHR₁—CHR₂—O)_(n)— moiety or        chain.

The term “—(CHR₁—CHR₂—O)_(n)— moiety” is used when n=1 and term“—(CHR₁—CHR₂—O)_(n)— chain” is used when n<1.

The (*) signs in formula (III) are intended to show that the moieties—(N—R₃—CO)_(n)— form a polymeric chain and “x” in formula (III) is thenumber of repeating —(CHR₁—CHR₂—O)— moieties in a polymeric chain,wherein chains with different x can be present.

With respect to special embodiments and combinations of n, R₁ and R₂ itis referred to the above disclosure as to formula (I).

In one embodiment, which can be combined with all special embodimentsand combinations of n, R₁, and R₂, R₃ is C₂-C₂₀-alkylene, preferablyC₂-C₁₂-alkylene, unsubstituted or substituted by 1, 2, 3, 4, 5 or 6substituents selected independently of one another from the groupconsisting of alkylene, cycloalkylene and arylene.

In a preferred embodiment, R₃ is an alkylene residue of the formula—(CH₂)_(y)—, wherein y is an integer form 2 to about 20, more preferably2 to about 12, and most preferably 2 to about 7.

A polyamide as described above can, for example, be prepared byring-opening polymerization of a previously described lactam, or byring-opening co-polymerization of at least two of the previouslydescribed lactams.

Other polyamides which can be employed in the present invention arepolyamides which are prepared from dicarboxylic acids and diamines andwhich are alkoxylated at one or more of their nitrogen atoms with one ormore residues of formula (I) as described above. An example is, withoutrestriction, N-alkoxylated Polyamide 6,6, prepared from adipic acid andhexamethylene diamine.

Another suitable polyamide is N-alkoxylated Polyamide 6, particularlyN-ethoxylated Polyamide 6, which can be prepared from N-alkoxylated,particularly N-ethoxylated ε-caprolactame.

Polyamides of formula (III) can be prepared from alkoxylated lactams.Alkoxylated lactams are described in DE3836521, which is incorporated byreference in its entirety.

The nitrogen containing adhesion-promoting compound that is used ascomponent d) in the solution of the invention can be a fatty amine whichis connected at one or more of its nitrogen atoms with a residue offormula (I) as described above.

Before the residue of formula (I) is attached to the nitrogen atom ofthe fatty amine, the fatty amine in the present invention is a fattyamine of the general formula R₇NH₂ or a fatty amine with the generalformula R₇R₈NH, wherein R₇ and R₈ are independently from each otheraliphatic residues, preferably with 2 to about 40 carbon atoms. Fattyamines are obtainable from fatty acids, i.e. by reacting fatty acidswith ammonia to obtain fatty nitriles, and reacting the fatty nitrileswith hydrogen to obtain fatty amines.

The term “fatty acid” means, in the meaning of the present invention, acarboxylic acid with an aliphatic chain, which can, according to theabove definition, be saturated or unsaturated, and branched orunbranched. Preferably a fatty acid in the meaning of the presentinvention contains at least 2 carbon atoms, including the carboxylC-atom. Fatty acids can encompass naturally occurring fatty acids,hardened fatty acids, modified naturally fatty acids, and syntheticallyproduced fatty acids.

After introduction of one residue of formula (I) to a fatty amine offormula R₇NH₂, a secondary amine is formed as the adhesion-promotingcompound. After introduction of two residues of formula (I) to a fattyamine of formula R₇NH₂, a tertiary amine is formed as the finaladhesion-promoting compound. After introduction of one residue offormula (I) to a secondary fatty amine (R₇R₈NH), a tertiary amine isformed as the adhesion-promoting compound.

The nitrogen containing, adhesion-promoting compound, particularly thefatty amine which is connected at its nitrogen atom with at least oneresidue of above formula (I), is a non-quaternary amine compound. Inother words, a fatty amine as employed in the present invention, whichis connected at its nitrogen atom with at least one residue of formula(I), does not contain, or is not, a quaternary ammonium cation.

Quaternary amine compounds contain a quaternary ammonium cation, whichis positively charged and has the general structureN(R′)(R″)(R′″)(R″″)⁺, wherein R′, R″, R′″ and R″″ are hydrocarbonresidues, which can be equal or different from each other and which maycontain heteroatoms such as oxygen and nitrogen. Unlike the ammonium ion(NH₄ ⁺) and the primary (NH₃(R′)⁺), secondary (NH₂(R′)(R″)⁺), ortertiary (NH(R′)(R″)(R″″)⁺) ammonium cations, the quaternary ammoniumcations are permanently charged, independent of pH.

The nitrogen-containing, adhesion-promoting compound selected forcomponent d) of a solution of the invention is in one embodiment of thepresent invention a fatty amine of formula (IV)

-   -   wherein    -   n and m are independently from each other an integer from 1 to        about 100,    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can be selected        independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—        moiety, and    -   R₄ is an aliphatic residue with 2 to about 40 carbon atoms,

With respect to special embodiments and combinations of R₁ and R₂ it isreferred to the above disclosure of formula (I). n and m areindependently from each other preferably 1 to about 50.

In one embodiment, which can be combined with all special embodimentsand combinations of n, m, R₁ and R₂, R₄ is a C₁₂ to C₂₄ aliphaticresidue, wherein the term aliphatic, as already defined above,encompasses saturated and unsaturated, straight chain and branchedresidues. Most preferably, R₄ is a saturated or unsaturated straightchain C₁₂ to C₂₄ aliphatic residue.

Compounds of formula (IV) can be obtained by alkoxylation of primaryfatty amines with the general formula R₄—NH₂, wherein R₄ is defined asabove.

In one embodiment a mixture of compounds of formula (IV) with differentresidues R₄ is employed wherein the compounds of formula (IV) can beprepared by alkoxylation of a mixture of primary fatty amines withdifferent residues R₄. The mixture of amines can be obtained from amixture of different fatty acids which is reacted to fatty amines inknown manner. A mixture of different fatty acids can be obtained from anatural source, as for example animal fats or vegetable oils. Examplesfor vegetable oils are Palm, Soybean, Rapeseed, Sunflower seed, Peanut,Cottonseed, Palm kernel, Coconut, Olive, Corn, Grape seed, Hazelnut,Linseed, Rice bran, Safflower and Sesame oil. Examples for animal fatsare tallow, as for example beef tallow, mutton tallow, hardened tallow,and (pig) lard.

In a special embodiment, the compound of formula (IV) is an alkoxylatedtallowamine, or an alkoxylated hydrogenated tallowamine. The term“hydrogenated” tallowamine means a tallowamine, wherein unsaturatedbonds in fatty acid residues have been transformed to saturated bonds byhydrogenation. In this embodiment n and m in formula (IV) are preferablyindependently from each other an integer from 1 to about 50 and R₁ andR₂ are preferably hydrogen.

The term “tallowamine” means a mixture of fatty amines which is obtainedfrom tallow. For producing tallowamines tallow is converted to fattyacids by reactions that are known to an expert skilled in the art, i.e.saponification, and the thus obtained fatty acids are in another stepconverted to fatty amines by reactions that are known to an expertskilled in the art (c.f. “Fettamine” in Römpp Chemielexikon, Thieme,1989-1992, ISBN 3-13-102759-2).

In one embodiment, the tallowamine which is basis for the compound offormula (IV) is made from a fatty acid composition obtained from tallow,comprising in weight-%:

-   Oleic acid: 38-47%-   Palmitic acid: 22-28%-   Stearic acid: 14-22%-   Palmitoleic acid: 2-5%-   Myristic acid: 2-5%-   Linoleic acid: 2-5%-   Margaric acid: 1-4%-   Pentadecanoic acid: 1-2%-   Myristoleic acid: 0-1%-   Linolenic acid: 0-1%-   Arachidic acid: 0-1%-   Behenic acid: 0-1%

In another embodiment, the tallowamine which is basis for the compoundof formula (IV) is made from a fatty acid composition obtained fromhydrogenated tallow, comprising in weight-%:

-   Stearic acid: 50-55%-   Palmitic acid: 28-32%-   Myristic acid: 2-6%-   Margaric acid: 1-4%-   Pentadecanoic acid: 0.5-2%-   Arachidic acid: 0.5-2%

Preferred fatty amines and tallowamines that can be employed in thepresent invention Berol 387™, Ethomeen OV/22™ and Ethomeen HT/60™,Products and Trademarks by Akzo-Nobel. Details as to these compounds arepresented in the examples.

The nitrogen-containing, adhesion-promoting compound selected forcomponent d) of a solution of the invention is in another embodiment ofthe present invention a fatty amine of formula (V)

-   -   wherein    -   n is an integer from 1 to about 100,    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can be selected        independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—        moiety, and    -   R₄ and R₅ are independently from each other an aliphatic residue        with 2 to about 40 carbon atoms.

With respect to special embodiments and combinations of n, R₁ and R₂ itis referred to the above disclosure of formula (I).

In one embodiment, which can be combined with all special embodimentsand combinations of n, R₁ and R₂, R₄ and R₅ are independently from eachother a C₁₂ to C₂₄ aliphatic residue, wherein the term aliphatic, asalready defined above, encompasses saturated and unsaturated, straightchain and branched, residues. Most preferably, R₄ and R₅ areindependently from each other a saturated or unsaturated straight chainC₁₂ to C₂₄ aliphatic residue.

Compounds of formula (V) can be obtained by alkoxylation of secondaryfatty amines with the general formula (R₄)(R₅)NH, wherein R₄ and R₅ aredefined as above.

In one embodiment a mixture of compounds of formula (V) is employedwherein the compounds of formula (V) can be prepared by alkoxylation ofa mixture of different secondary fatty amines. A mixture of secondaryfatty acid amines can be obtained from a mixture of different fattyacids which is reacted to secondary fatty amines in known manner. Asstated above a mixture of different fatty acids can be obtained from anatural source, as for example the above mentioned animal fats orvegetable oils.

In a special embodiment, the compound of formula (V) is an alkoxylatedtallowamine or an alkoxylated hydrogenated tallowamine. In thisembodiment n in formula (V) is preferably an integer from 1 to about 50and R₁ and R₂ are preferably hydrogen. In this connection tallows asdescribed above can be employed as starting material for producingtallowamine.

The nitrogen-containing, adhesion-promoting compound selected forcomponent d) of a solution of the invention is in still anotherembodiment of the present invention an amide of formula (VI):

-   -   wherein    -   n and m are independently from each other an integer from 1 to        about 100,    -   R₁ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   R₂ is hydrogen or a hydrocarbon residue with 1 to about 6 carbon        atoms,    -   each R₁ and R₂ in a —(CHR₁—CHR₂—O)— moiety can be selected        independently of each R₁ and R₂ in another —(CHR₁—CHR₂—O)—        moiety, and    -   R₆ is an aliphatic residue with 1 to about 39 carbon atoms,

With respect to special embodiments and combinations of R₁ and R₂ it isreferred to the above disclosure of formula (I). n and m areindependently from each other preferably 1 to about 50.

In one embodiment, which can be combined with all cited embodiments andcombinations of n, m, R₁ and R₂, R₆ is a C₁₁ to C₂₃ aliphatic residue,wherein the term aliphatic, as already defined above, encompassessaturated and unsaturated, straight chain and branched residues. Mostpreferably, R6 is a saturated or unsaturated straight chain C₁₁ to C₂₃aliphatic residue.

The acid which is used as component b) of the solution of the inventionis preferably an inorganic acid or mineral acid, as sulfuric acid,hydrochloric acid, nitric acid, phosphoric acid, most preferablysulfuric acid. Other acids can also be employed. The acid is nosulphinic, selenic or telluric acid.

The nitrogen-containing, five-member heterocyclic compounds which isemployed as component c) of the solution of the invention can bemonocyclic and polycyclic condensed ring systems. For example, thecompounds can contain an anellated benzene, naphthalene or pyrimidinering. When selecting these compounds, make sure that they aresufficiently soluble in the acid solution. It is preferable for thesolution to contain triazoles, tetrazoles, imidazoles, pyrazoles andpurines or their derivatives.

In particular, the solution contains triazoles of chemical formula(VIIa):

with R₁₇, R₁₈=hydrogen, alkyl, substituted alkyl, amino, phenyl,substituted phenyl, carboxyalkyl, where R₁₇ and R₁₈ can be the same ordifferent and can be a part of the homo or heterocyclic ring condensedonto the triazole ring.

Benzotriazole, methylbenzotriazole, ethylbenzotriazole anddimethylbenzotriazole are particularly preferable.

In addition, the solution can contain tetrazoles of chemical formula(VIIb):

with R₁₉=hydrogen, alkyl, substituted alkyl, halogenalkyl, amino,phenyl, substituted phenyl, benzyl, carboxy, carboxyalkyl,alkoxycarbonyl, aminocarbonyl, R₂₀—CONH with R₂₀=hydrogen, alkyl,substituted alkyl, phenyl or substituted phenyl.

Preferred tetrazole compounds may be 5-aminotetrazole and5-phenyltetrazole. A preferred imidazole compound may be benzimidazole.5-aminotetrazole, 5-phenyltetrazole, benzotriazole, methylbenzotriazoleand ethylbenzotriazole are preferred compounds given their favorablesolubility in the pretreatment solution and their availability.

Preferred combinations are benzotriazole, methylbenzotriazole,ethylbenzotriazole, 5-aminotetrazole and 5-phenyltetrazole as thenitrogen-containing, heterocyclic compounds with aminothiophenecarboxylic acids, their esters and amides, aminothiazoles andsubstituted aminothiazoles as the heterocyclic compounds.

The nitrogen-containing, five-membered, heterocyclic compound selectedfor component c) in the solution preferably contains no sulphur atom, noselenium atom or tellurium atom in the heterocycle.

The solution of the present invention can comprise, as a furthercomponent in addition to above mentioned components a)-d), at least onesulphur, selenium or tellurium-containing bonding compound which isselected from the group comprising sulphinic acids, selenic acids,telluric acids, heterocyclic compounds which contain at least onesulphur, selenium and/or tellurium atom in the heterocycle, sulphoniumsalts, selenonium salts and telluronium salts, the sulphonium,selenonium and telluronium salts being compounds having the generalformula (VIII):

-   -   wherein    -   A=S, Se or Te,    -   R₉, R₁₀ and R₁₁ are alkyl, substituted alkyl, alkenyl, phenyl,        substituted phenyl, benzyl, cycloalkyl, substituted cycloalkyl,        R₉, R₁₀ and R₁₁ being identical or different, and Z=anion of an        inorganic or organic acid or hydroxide.

If a sulphur, selenium or tellurium-containing bonding compound asmentioned above is added as a further component, the acid selected forcomponent b) in the solution is in any case not identical to thesulphinic, selenic or telluric acids selected for the sulphur, seleniumor tellurium containing bonding compound, and the nitrogen-containing,five-membered, heterocyclic compound selected for component c) in thesolution contains no sulphur atom, no selenium atom or tellurium atom inthe heterocycle.

Preferred sulfinic acids are compounds of chemical formula (IX)

with R₁₂, R₁₃ and R₁₄=hydrogen, alkyl, substituted alkyl, phenyl,substituted phenyl or R₁₅—(CO)— with R₁₅=hydrogen, alkyl, substitutedalkyl, phenyl or substituted phenyl, where R₁₂, R₁₃ and R₁₄ can be thesame or different, and aromatic sulfinic acids.

It is preferable for the solution to contain formamidine sulfinic acidas the bonding compound. Preferable aromatic sulfinic acids are benzenesulfinic acid, toluene sulfinic acids, chlorobenzene sulfinic acids,nitrobenzene sulfinic acids and carboxybenzene sulfinic acids.

Other preferable heterocyclic bonding compounds are thiophene, thiazole,isothiazole, thiadiazole and thiatriazole.

Suitable thiophenes are compounds of chemical formula (X):

with R₂₁, R₂₂, R₂₃, R₂₄=hydrogen, alkyl, substituted alkyl, phenyl,substituted phenyl, halogen, amino, alkylamino, dialkylamino, hydroxy,alkoxy, carboxy, carboxyalkyl, alkoxycarbonyl, aminocarbonyl, R₂₅—CONH—with R₂₅=hydrogen, alkyl, substituted alkyl, phenyl or substitutedphenyl, where R₂₁, R₂₂, R₂₃ and R₂₄ can be the same or different and canbe a part of homo or heterocyclic rings condensed onto the thiophenering.

Particularly preferred thiophenes are aminothiophene carboxylic acids,their esters and amides. For example, 3-aminothiophene-2-carboxylic acidmethyl ester can be advantageously used.

Suitable thiazoles are compounds of chemical formula (XI):

with R₂₆, R₂₇, R₂₈=hydrogen, alkyl, substituted alkyl, phenyl,substituted phenyl, halogen, amino, alkylamino, dialkylamino, hydroxy,alkoxy, carboxy, carboxyalkyl, alkoxycarbonyl, aminocarbonyl, R₂₉—CONH—with R₂₉=hydrogen, alkyl, substituted alkyl, phenyl or substitutedphenyl, where R₂₆, R₂₇ and R₂₈ can be the same or different and can be apart of homo or heterocyclic ring condensed onto the thiazole ring.

Particularly suitable thiazoles are aminothiazole and substitutedaminothiazole.

Other preferred thiadiazole bonding compounds are from the group,consisting of aminothiadiazoles and substituted aminothiadiazoles.

In addition, the preferred sulfonium salts used as bonding compounds aresalts of trimethylsulfonium, triphenylsulfonium, methioninealkylsulfonium and methionine benzylsulfonium.

A further optional component in the solution of the present inventionare chloride ions, preferably in concentration of Cl⁻ of 5-500 mg/l,more preferably 10-50 mg/l.

A preferred solvent for the solution is water. Other organic solventslike alcohols, can be added, e.g. to increase the solubility of thecontained components, especially the nitrogen-containing, five-memberheterocyclic compounds and the sulphur, selenium or tellurium-containingbonding compound.

To stabilize hydrogen peroxide against decomposition, the solution cancontain stabilizing compounds, such as p-phenolsulfonic acid.

In addition, other inorganic and organic compounds can be in thesolutions, e.g., copper sulfate and wetting agents.

In a further aspect the present invention is directed to a method forthe pre-treatment of a copper surface for the subsequent formation of afirmly adhesive bonding between the copper surfaces and plasticsmaterial substrates, wherein the copper surface is brought into contactwith

-   a) hydrogen peroxide,-   b) at least one acid,-   c) at least one nitrogen-containing, five-membered, heterocyclic    compound, and-   d) at least one nitrogen-containing, adhesion-promoting compound    which is selected from the group comprising lactams, non-quaternary    fatty amines, amides and polyamides, which is connected at one or    more of its nitrogen atoms with at least one residue of formula (I)    as defined above.

With respect to components a)-d) that are employed in the method of theinvention it is referred to the previous disclosure, including allspecific and preferred embodiments.

The term “copper surface” is intended to also include multiple coppersurfaces. Thus, the method of the present invention encompassessimultaneous treatment of multiple copper surfaces.

The process according to the invention is an extremely easy way topretreat copper surfaces to allow them to tightly bond with plastics.The adhesion does not decrease even after a long time. If theadhesion-promoting compound(s) as described above is not in thesolution, such bond strength cannot be attained. In addition, thelong-term stability of the bond after treating the copper with solutionwithout the invention's adhesion-promoting compounds is substantiallylower than when the adhesion-promoting compound is used.

In addition, the problems that arise in conjunction with platingthrough-holes in printed circuit boards (i.e., the formation of pinkring and wedge voids) are avoided by using the additionaladhesion-promoting compound in the treatment solution. Theadhesion-promoting layers created using the solution according to theinvention have an excellent acid resistance, whereas black oxide andreduced black oxide layers are somewhat sensitive to hydrochloric acidsolutions. It has even been shown that the adhesion of copper to organicsubstrates can be improved in certain cases when the copper surfaces aretreated with diluted acid after being treated with components a)-d) asdescribed above and before the bond is created. It is preferable to usean inorganic acid or mineral acid, as sulfuric acid, hydrochloric acid,nitric acid, phosphoric acid, most preferably sulfuric acid.

The copper surface is preferably cleaned to ensure that the pretreatmentaccording to the invention is effective. Any conventional cleaningsolution can be used. Normally, wetting agents and sometimes complexer(such as triethanol-amine)-containing aqueous solutions are used.

After the cleaned copper surface is rinsed, it can be brought intocontact with a so-called predipping solution, also abbreviated as“predip”, that contains one of the five-member heterocyclic compounds(component c), preferably at a concentration of 0.1-10 g/l, andespecially 0.5-2 g/l. This treatment helps the adhesion-promoting layerto be formed in the subsequent treatment step. In particular, any delaysin the formation of the layer are avoided. The surface(s) is/are thentreated with components a)-d) without being rinsed beforehand.

The present invention discloses two preferred embodiments how thepre-treatment with components a)-d) can be performed. In the firstpreferred embodiment, a copper surface is treated with all componentsa)-d) at the same time with one solution. In the second preferredembodiment, a copper surface is treated sequentially with two solutions,the first solution comprising or containing components a)-c) and thesecond solution comprising or containing component d).

In the first preferred embodiment of the method of the invention thecopper surface is brought into contact with the above-described solutioncomprising components a)-d). In this connection, all embodiments andpreferred embodiments of the solution can be employed in the method. Inthe first embodiment of the method of the invention, basically one stepis necessary, i.e., treating the copper surface with the solutionaccording to the invention to allow them to bond with organicsubstrates.

As the adhesion-promoting layer is formed, the copper surfaces changecolor, usually from pink to a brown tint, depending on the combinationof nitrogen-containing, five-member heterocyclic and adhesion-promotingcompounds.

The microetching by the hydrogen peroxide in connection with the acidyields microrough copper surfaces. Since this increases the surfacearea, the subsequent adhesion of the copper surfaces to the plasticsubstrate also increases. The change in color of the surface duringtreatment is caused by a thin copper oxide layer. It is also suspectedthat the adhesion is also improved by the formation of a copper organiccompound that forms on the copper surface and probably consists ofcopper or copper oxide, the five-membered, heterocyclic compound, andthe nitrogen-containing adhesion-promoting compound. It is preferablefor the acid in the solution according to the invention to be aninorganic acid, and especially sulfuric acid. Other acids can of coursebe used.

The treatment is preferably carried out at 20-60° C. The treatment timeis preferably 10-600 sec. The higher the temperature, the faster-actingthe solution. The treatment times can hence even be much shorter. From apractical standpoint, a preferable average temperature would be 25-45°C. to better control the reaction. Average treatment times are 20-90seconds.

In addition, a top temperature limit may have to be set due to possibleincompatibilities between certain solution components at hightemperatures, e.g., wetting agents that have difficulty dissolving athigh temperatures.

The preferable concentration ranges in the solution are:

Acid, preferably sulfuric acid conc. 10-250 g/l Hydrogen peroxide, 30weight percent 1-100 g/l (corresponds to hydrogen peroxide 0.3-30 g/l)concentration of N-containing, five-membered, 0.5-50 g/l heterocycliccompound Nitrogen-containing, adhesion- promoting compound lactam0.05-10 g/l, preferably 0.1-6 g/l non-quaternary fatty amine 0.05-10g/l, preferably 0.1-6 g/l amide 0.05-10 g/l, preferably 0.1-6 g/lpolyamide 0.05-10 g/l, preferably 0.1-6 g/l

As stated before, mixtures of different lactams, different fatty amines,different amides, and different polyamides as well as mixtures of two ormore of a lactam, non-quaternary fatty amine, amide and polyamide can beemployed. If different lactams, fatty amines, different amides, orpolyamides are employed, the above concentration range of a component(e.g. lactam) means the total concentration range of the component ormixture of components (e.g. lactam or mixture of lactams). Preferably,the total concentration of a nitrogen-containing adhesion-promotingcompound does not exceed 10 g/l.

The optimum concentrations for the cited bath components depend on thetype of five-membered heterocyclic compounds and nitrogen-containingadhesion-promoting compounds.

To increase the useful life of the solution, it is a good idea toprepare the ready-for-use treatment solution right before carrying outthe procedure. For example, hydrogen peroxide can be mixed with asulfuric acid solution of the five-membered heterocyclic compound andthe nitrogen-containing adhesion-promoting compound, or a preparedsolution can be supplemented directly before use to set the desiredconcentrations of individual components.

In the second preferred embodiment of the method of the invention acopper surface is in a first step brought into contact with a firstsolution, comprising

-   -   a) hydrogen peroxide,    -   b) at least one acid, and    -   c) at least one nitrogen-containing, five-membered, heterocyclic        compound and in a second step a copper surface is brought into        contact with a second solution, comprising    -   d) at least one nitrogen-containing, adhesion-promoting compound        which is selected from the group comprising lactams,        non-quaternary fatty amines, amides and polyamides, which is        connected at one or more of its nitrogen atoms with at least one        residue of formula (I) as defined above.

The nitrogen-containing, adhesion-promoting compound of the secondsolution is equal to component d) as described above. Therefore it isreferred to all embodiments and preferred embodiments of component d).

Surfaces are treated with the first solution according to the inventioncontaining components a), b) and c) without being rinsed. The substratescan then be rinsed to remove any adhering liquid from the substrate.Subsequently, the surface is treated with second solution comprisingcomponent d). The second solution is in the present invention and in theappended examples also called “postdipping solution” or just “postdip”.The copper surfaces can also be treated with the second solutiondirectly after being treated with the first solution without beingrinsed.

With this treatment, the copper surfaces change color from pink to brownas an adhesion-promoting layer is formed depending on the combination ofnitrogen-containing, five-member heterocycle in the first solution andadhesion-promoting compounds in the second solution.

It is preferable for the acid in the first solution to be an inorganicacid, especially sulfuric acid. Of course other acids can be used.

To stabilize hydrogen peroxide against decomposition, other additionalcompounds can be used in the first solution such as p-phenolsulfonicacid.

Both solutions can contain solvents such as water and additional otherorganic solvents like alcohols, e.g. to increase the solubility of thecontained components, especially the nitrogen-containing, five-memberheterocyclic compounds and the adhesion-promoting compounds.

In addition, other inorganic and organic compounds can be in thesolutions, e.g., wetting agents. Copper sulfate can also be in thesecond solution.

The treatment with the two solutions is preferably carried out at 20-60°C. The treatment time is preferably 5-600 s. The higher the temperature,the faster-acting the solution. The treatment times may hence be evenmuch shorter. From a practical standpoint, an average temperature ispreferably selected such as 25-45° C. to better control the reaction.Average treatment times are 10-60 seconds. In addition, a toptemperature limit may have to be set due to possible incompatibilitiesbetween certain components in the solution at high temperatures, e.g.,wetting agents that dissolve with difficulty at high temperatures.

The preferable concentration ranges in the solutions are:

First Solution:

Acid, preferably sulfuric acid conc. 10-250 g/l Hydrogen peroxide, 30weight percent 1-100 g/l (corresponds to hydrogen peroxide concentrationof 0.3-30 g/l) N-containing, five-membered, heterocyclic compound 0.5-50g/l

Second Solution:

Nitrogen-containing, adhesion-promoting compound lactam 0.05-10 g/l,preferably 0.1-6 g/l non-quaternary fatty amine 0.05-10 g/l, preferably0.1-6 g/l amide 0.05-10 g/l, preferably 0.1-6 g/l polyamide 0.05-10 g/l,preferably 0.1-6 g/land optionally an acid, preferably an inorganic acid, most preferablysulfuric acid, in a concentration of 10-250 g/l.

As stated before, mixtures of different lactams, different fatty amines,different amides, and different polyamides as well as mixtures of two ormore of a lactam, non-quaternary fatty amine, amide and polyamide can beemployed. If different lactams, fatty amines, different amides, orpolyamides are employed, the above concentration range of a component(e.g. lactam) means the total concentration range of the component ormixture of components (e.g. lactam or mixture of lactams). Preferably,the total concentration of a nitrogen-containing, adhesion-promotingcompound does not exceed 10 g/l.

The optimum concentrations for the cited bath components depend on thetype of nitrogen-containing heterocyclic compounds andadhesion-promoting compounds.

To increase the storage life of the first and second solution of theinvention, it is a good idea to prepare the ready-for-use treatmentsolutions right before carrying out the procedure. For example, thefirst solution can be created by mixing hydrogen peroxide with asulfuric acid solution of the nitrogen-containing heterocyclic compound,or a prepared solution can be supplemented directly before use to reachthe desired concentrations of individual components.

After having carried out the method of the invention the copper surfacesare rinsed, preferably with warm, deionized water. Then they are dried,e.g. with hot air.

The workpieces with the copper surfaces can be treated in conventionaldipping systems. In an alternative for treating the printed circuitboards, it is particularly good to use so-called continuous systems. Theboards are guided along a horizontal transport path through the system.They are brought into contact with the treatment solutions by guidingthem through a liquid bed between squeezing rollers located at thebeginning and end of the treatment path, and/or bringing them intocontact with the treatment liquid using suitable nozzles such as sprayor surge nozzles. The printed circuit boards can be held in a horizontalor vertical position or at any other angle.

The following examples serve further to clarify the invention:

EXAMPLES

Duraver 104 ML epoxy based 18 μm copper layer cladded innerlayermaterial (manufacturer: Isola) was treated according to the followingprocess sequence.

At first the samples were treated with a cleaner solution BondFilm®Cleaner Alk (Atotech Deutschland GmbH) for 5 min at 50° C. Afterwardsthe sample was rinsed and etched with an alternative oxide compositionaccording to the formulations in the following examples for 60-70seconds at 35° C. The treatment time was adjusted in order to have acomparable etch depth of 1.2 μm for all test specimen. After rinsingagain the sample is dried. The complete set of etched samples showed abrown to dark brown surface cosmetic.

All samples were laminated in a multilayer press with a Duraver 104 MLepoxy based prepreg layer according to the material data sheet(manufacturer: Isola). During this procedure the semi cured epoxyprepreg layer is cured and bonded to the treated copper metal surface.

Finally, the adhesion between the micro roughend copper surface and theepoxy polymer was measured. Peel strength values were measured accordingto the method described in IPC-™-650 Test Methods Manual Number 2.4.8revision C.

Example 1 Comparative Example

The following aqueous formulation was prepared:

Benzotriazole 10 g/l Hydrogen peroxide 35% 30 g/l Sulfuric acid 50% 186g/l Chloride ions 20 mg/l

A peel strength value of 7.5 N/cm was measured after using a treatmenttime of 60 seconds and successive lamination of a prepreg layer.

Example 2

The solution of example 1 was used except that 1.25 g/l N-ethoxylatedPolyamide 6, obtainable from ε-Caprolactamhexaethoxylate monomer, wasadded to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 9.5 N/cm was measured.

Example 3a

The solution of example 1 was used except that 0.01 g/l of a tallowamine having a residue according to formula (I) with R₁ and R₂=hydrogenand n=40 (Berol 387®, Akzo Nobel) was added to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 8.0 N/cm was measured.

Example 3b

The solution of example 1 was used except that 0.05 g/l of a tallowamine having a residue according to formula (I) with R₁ and R₂=hydrogenand n=40 (Berol 387®, Akzo Nobel) was added to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 8.7 N/cm was measured.

Example 3c

The solution of example 1 was used except that 0.1 g/l of a tallow aminehaving a residue according to formula (I) with R₁ and R₂=hydrogen andn=40 (Berol 387®, Akzo Nobel) was added to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 8.7 N/cm was measured.

Example 3d

The solution of example 1 was used except that 0.2 g/l of a tallow aminehaving a residue according to formula (I) with R₁ and R₂=hydrogen andn=40 (Berol 387®, Akzo Nobel) was added to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 9.5 N/cm was measured.

Example 3e

The solution of example 1 was used except that 0.5 g/l of a tallow aminehaving a residue according to formula (I) with R₁ and R₂=hydrogen andn=40 (Berol 387®, Akzo Nobel) was added to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 10.3 N/cm was measured.

Example 4

The solution of example 1 was used except that 0.5 g/l of a hydrogenatedtallow alkylamine having a residue according to formula (I) with R₁ andR₂=hydrogen and n=50 (Ethomeen HT/600®, Akzo Nobel) was added to saidsolution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 10.3 N/cm was measured.

Example 5

The solution of example 1 was used except that 0.5 g/l of aoleylaminethoxylate (a tertiary amine based on a primary oleyl aminehaving a residue according to formula (I) with R₁ and R₂=hydrogen andn=12) (Ethomeen® OV/22, Akzo Nobel) was added to said solution.

After using a treatment time of 70 seconds and successive lamination ofa prepreg layer a peel strength value of 9.4 N/cm was measured.

Example 6

A sample treated with a solution according to example 1 was thenimmersed into an aqueous post dip solution of 1.25 g N-ethoxylatedPolyamide 6, obtainable from ε-Caprolactamhexaethoxylate for 30 secondsat 25° C.

After successive lamination of a prepreg layer a peel strength value of8.9 N/cm was measured.

Example 7

A sample treated with a solution according to example 1 was thenimmersed into an aqueous post dip solution of 0.2 g N-ethoxylatedPolyamide 6, obtainable from ε-Caprolactamhexaethoxylate for 30 secondsat 25° C.

After successive lamination of a prepreg layer a peel strength value of8.3 N/cm was measured.

The invention claimed is:
 1. A solution, comprising: a) hydrogenperoxide; b) an acid; c) a nitrogen-containing, five-membered,heterocyclic compound; and d) a lactam or a polyamide, which isconnected at one or more of its nitrogen atoms with at least one residueof formula (I):

wherein: n is an integer from 1 to 100; R₁ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; R₂ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; and each R₁ and R₂ in a—(CHR₁—CHR₂—O)— moiety is selected independently of each R₁ and R₂ inanother —(CHR₁—CHR₂—O)— moiety; with the proviso that the compound of c)is not connected at any of its nitrogen atoms with a residue of formula(I).
 2. The solution of claim 1, wherein the compound of d) is a lactamof formula (II);

wherein: n is an integer from 1 to 100; R₁ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; R₂ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; each R₁ and R₂ in a —(CHR₁—CHR₂—O)—moiety is selected independently of each R₁ and R₂ in another—(CHR₁—CHR₂—O)— moiety; and R₃ is a hydrocarbon residue with 1 to 20carbon atoms.
 3. The solution of claim 1, wherein the compound of d) isa polyamide of formula (III):

wherein: n is an integer from 1 to 100; R₁ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; R₂ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; each R₁ and R₂ in a —(CHR₁—CHR₂—O)—moiety is selected independently of each R₁ and R₂ in another—(CHR₁—CHR₂—O)— moiety; R₃ is a hydrocarbon residue with 1 to 20 carbonatoms, each R₃ in a —(N—R₃—CO)— moiety is selected independently of eachR₃ in another —(N—R₃—CO)— moiety; and each n in a —(CHR₁—CHR₂—O)_(n)—moiety or chain is selected independently of each n in another—(CHR₁—CHR₂—O)_(n)— moiety or chain.
 4. The solution of claim 2, whereinR₃ is an alkylene residue with the formula —(CH₂)_(y)—, and wherein y isan integer from 2 to
 12. 5. The solution of claim 1, wherein thesolution comprises a sulphur, selenium or tellurium-containingadhesion-promoting compound, said compound being a sulphinic acid,selenic acid, telluric acid, heterocyclic compound that comprises atleast one sulphur, selenium and/or tellurium atom in the heterocycle,sulphonium salt, selenonium salt or telluronium salt, wherein thesulphonium salt, selenonium salt or telluronium salt has a generalformula (VIII);

wherein: A is S, Se or Te; R₉, R₁₀ and R₁₁ are independently alkyl,substituted alkyl, alkenyl, phenyl, substituted phenyl, benzyl,cycloalkyl, or substituted cycloalkyl; and Z⁻ is an anion of aninorganic or organic acid or hydroxide; with the proviso that the acidof b) is not identical to the sulphinic, selenic or telluric acidsselected for the sulphur, selenium or tellurium containingadhesion-promoting compound, and that the compound of c) contains nosulphur atom, selenium atom or tellurium atom in the heterocycle.
 6. Amethod for pre-treating a copper surface for the subsequent formation ofa firmly adhesive bond between the copper surface and a plastic materialsubstrate, the method comprising contacting the copper surface with asolution comprising: a) hydrogen peroxide; b) an acid; c) anitrogen-containing, five-membered, heterocyclic compound; and d) alactam or a polyamide, which is connected at one or more of its nitrogenatoms with at least one residue of formula (I)

wherein n is an integer from 1 to 100; R₁ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; R₂ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; and each R₁ and R₂ in a—(CHR₁—CHR₂—O)— moiety is selected independently of each R₁ and R₂ inanother —(CHR₁—CHR₂—O)— moiety; with the proviso that the compound of c)is not connected at any of its nitrogen atoms with a residue of formula(I).
 7. The method of claim 6, wherein the copper surface is broughtinto contact with the solution.
 8. A method of pre-treating a printedcircuit board inner layer which has a copper layer, the methodcomprising contacting the printed circuit inner layer or a syntheticresin layer with the solution of claim 1, and forming a firmly adhesivebond between the printed circuit inner layer and the synthetic resinlayer.
 9. The method of claim 8, wherein the solution comprises a lactamor a polyamide, which is connected at one or more of its nitrogen atomswith at least one residue of formula (I):

wherein: n is an integer from 1 to 100; R₁ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; R₂ is hydrogen or a hydrocarbonresidue with 1 to 6 carbon atoms; and each R₁ and R₂ in a—(CHR₁—CHR₂—O)— moiety is selected independently of each R₁ and R₂ inanother —(CHR₁—CHR₂—O)— moiety.